Where music and home theatre is concerned, I’ve always been fascinated by bass – not LOUD bass, but low bass. These are the frequencies that convey the profound depth to pipe organ music, and the incredible power of a space shuttle launch. But they’re also among the most difficult frequencies for a home audio system to reproduce, requiring a lot of power and some heavy equipment.
When I graduated from college in ‘92, I received a subwoofer kit as a gift. All I had to do with build a simple sealed enclosure and do some wiring. I obliged, and came up with this:
It was a passive sub, siphoning the bass power out of the main signals for its own use, and then sending the rest on to the speakers. It worked reasonably well, and was definitely an improvement over my basic bookshelf speakers (Boston Acoustics A60’s), but it was still limited in the frequencies it could reproduce.
Cut to fall 2001, when a friend of mine invited me to a party at his coworker’s place. Turns out this guy was even more obsessed with bass than I was: he had done a great deal of research, and had actually built several subwoofers before settling on a design that produced awesome results. It was capable of high volume, and he loved to demonstrate it by playing the lobby gunfight from “The Matrix” during parties. But even more impressive, there seemed to be no limit to the depth of the sound: this thing was able to crank out frequencies at the threshold of hearing, sounds you felt rather than heard.
The gentleman was happy to share the design with me, and in fairly short order I set about building my own. The first step was to order the necessary parts:
The "heart" of this beast is a pair of 12-inch woofers. The "brain", also shown in the pic, is an onboard 150-watt amplifier with adjustable volume, adjustable cutoff frequency, and remote control.
The design of the enclosure looks something like this:
Basically, the two 12-inch woofers are mounted face-to-face as the boundary between a large chamber (bottom) and a small one (top). The woofers themselves never see the light of day; they’re hidden away inside the enclosure, and all of the sound is emitted by three ports (two from the upper chamber, one from the lower) that are open to atmosphere at the bottom of the rear panel.
The enclosure itself is built from 3/4" MDF, with joints held together by screws and wood glue. The ports are made of PVC pipe. In the construction photo below, the (open) top of the enclosure is facing the camera, and the back of the enclosure (with the ports and the square amplifier cutout) is facing up. You can see the routing of the PVC ports - the two lateral ports connect to the small upper chamber, and the center port connects to the large lower chamber.
Looking down into the (open) upper chamber, you can see one of the 12" drivers facing downward. Below it, a second 12" driver faces upwards; they are wired with opposite polarity so that they move together as a single unit. At the left , the circuit board for the front control panel can be seen.
The whole thing is covered with granite-texture formica:
The amp, hookups, and ports on the backside:
The large rectangular panel (with all the screws in it) provides access to the top chamber in the event that the drivers ever need to be replaced.
I’m particularly proud of this creation because I did it with very limited tools on hand. I had no table saw or router at the time, so cuts were made using a circular saw guided by a straightedge, and where panel edges overlapped, I filed them flush with a hand file.
Just like my friend’s original creation, this subwoofer delivers. Sound effects during movies command my attention, and when listening to music, I keep finding bass I never knew existed. It’s a slice of sonic heaven.
Questions? Comments? Email me!
©2006, Mitchell P. Patrie